Which is awkward when you’ve flown to his home in Ireland to interview him specifically about playing the physicist who oversaw the creation of the atomic bomb, later detonated over Hiroshima and Nagasaki. Murphy is under “strict instructions” not to talk about the content. Cillian Murphy is struggling with what he can and can’t say about his title role in Oppenheimer, the latest Christopher Nolan epic, such is the secrecy surrounding this film.